This invention relates to a centrifugal switch for effecting either an activation or deactivation of an electrical circuit. The centrifugal switch can be mounted on any suitable shaft for effecting the activation or deactivation of an electrical circuit such as for any speed responsive or speed sensitive control. Examples of such controls may include electrical motor starting circuits, fan switches for heating and air conditioning installations, and machine tool clutch circuits. The magnet controlled centrifugal switch of this invention is particularly useful in combination with a split-phase electrical motor so as to deactivate a starting winding thereof at a predetermined rotational speed, and will be described hereinafter with particular reference to that environment.
Heretofore, it has been the practice for centrifugal switches to utilize a fly weight type governor in combination with a spring type switch which is secured to a housing. To control the opening and closing of an electrical circuit at a desired shaft speed, washers or shims were used to fix the distal relationship of the switch to the housing. It was previously necessary to initially obtain a precise distal relationship between the switch and the housing for prior art centrifugal switches to properly function at desired shaft speeds. Also, when an electrical motor incorporating such a switch was rebuilt, it was necessary to reestablish the precise positioning of the switch and governor on the motor shaft or the switch would either function improperly or cease to function at all.
Aslo, due to susceptibility to dirt and grime, it has been the practice to position previous centrifugal switches within the housing of the electric motor for protection. Furthermore, as the switches were not interchangeable from one type of motor to another, it has been necessary to stock a variety of different switches for use with the associated variety of different electric motors.
Magnetically-operated centrifugal switches utilizing an attraction between opposite poles of two opposing and adjacent magnets for maintaining a circuit and relying upon centrifugal force to separate the magnets and consequently deactivate a circuit have also heretofore been known and used, but this type of switchh can develop an accumulation of dirt or grime on the faces of the opposing magnetic poles over time which will detrimentally affect the performance of the switch. The magnetically-operated centrifugal switch known heretofore has a tendency due to the aforesaid accumulation of dirt and grime to activate or deactivate an associated circuit prematurely since the centrifugal force will then more readily act to separate the opposed magnets thereof.
The centrifugal switch of the present invention overcomes the problems associated with the prior art switches. Dirt or grime on the faces of the adjacent and opposing magnets has no significant effect on the performance of the centrifugal switch thereby allowing for location either within the electric motor housing or even on the shaft external to said housing. Furthermore, the inventive switch is of a standardized construction so as to fit substantially all electric motors of the same shaft diameter.